Light-emitting device having a trench in a semiconductor layer

ABSTRACT

A light-emitting device comprises a substrate, an epitaxial structure formed on the substrate including a first semiconductor layer, a second semiconductor layer, and a light-emitting layer formed between the first semiconductor layer and the second semiconductor layer. A trench is formed in the epitaxial structure to expose a part of side surface of the epitaxial structure and a part of surface of the first semiconductor layer, so that a first conductive structure is formed on the part of surface of the first semiconductor layer in the trench, and a second conductive structure is formed on the second semiconductor layer. The first conductive structure includes a first electrode and a first pad electrically contacted with each other. The second conductive structure includes a second electrode and a second pad electrically contacted with each other. Furthermore, the area of at least one of the first pad and the second pad is between 1.5×10 4  μm 2  and 6.2×10 4  μm 2 .

REFERENCE TO RELATED APPLICATION

This application claims the right of priority based on U.S. patent application Ser. No. 12/292,593 entitled “Light-emitting Device”, filed on Nov. 21, 2008, which claims the right of priority based on Taiwan Patent Application No. 096144680, filed on Nov. 23, 2007, entitled “Light-emitting Device”, and is incorporated herein by reference and assigned to the assignee herein.

BACKGROUND OF THE APPLICATION

1. Technical Field

The present application relates to a light-emitting device, and in particular to a semiconductor light-emitting device.

2. Description of the Related Art

The light-emitting mechanism and the structure of a light-emitting diode (LED) are different from that of the conventional light sources. The LED has advantages of small size and high reliability, and has been widely used in different fields such as displays, laser diodes, traffic lights, data storage apparatus, communication apparatus, lighting apparatus, and medical apparatus.

Referring to FIGS. 1A and 1B. FIG. 1A is the schematic top view of a conventional nitride-based light-emitting device 1, and FIG. 1B illustrates a cross-sectional view of the conventional nitride-based light-emitting device 1 along the A-A′ line in the FIG. 1A. The conventional nitride-based light-emitting device 1 includes a substrate 11, an n-type nitride-based layer 12, a light-emitting layer 13, a p-type nitride-based layer 14, a p-type transparent electrode 15, an n-type electrode 16 having the function as a bonding pad, and a p-type bonding pad 17. The p-type bonding pad 17 is used for current injection. The current is injected through the p-type bonding pad 17 and moves to and spread through the p-type transparent electrode 15. Electrons and holes recombine in the light-emitting layer 13 and then produce photons. In fact, as shown in FIG. 1B, the current is crowded in the area where the p-type transparent electrode 15 is close to the n-type electrode 16 to cause a poor light-emitting efficiency. Besides, the temperature in the current crowded area is so high that the life of conventional nitride-based light-emitting device 1 is reduced.

In order to resolve above problems, a known art disclosed a light-emitting device 2 which is illustrated by a top view as shown in FIG. 2. Another known art also disclosed a light-emitting device 3 which is illustrated by a top view as shown in FIG. 3. Referring to FIG. 2, the light-emitting device 2 includes a p-type electrode and an n-type electrode. The p-type electrode includes a p-type bonding pad 24, two first armed electrodes 24 a extending from the p-type bonding pad 24, and second armed electrodes 24 b interposed between two first armed electrodes 24 a. The armed electrode can be used to decrease the light absorption of the p-type electrode. The current is injected from the p-type bonding pad 24 and spread by the armed electrodes. The n-type electrode includes an n-type bonding pad 25, third armed electrodes 25 a, and fourth armed electrodes 25 b. The current is injected from the p-type electrode, moves to the light-emitting region of the light-emitting device 2, and then flows to and out of the n-type electrode. The p-type armed electrodes 24 a, 24 b and the n-type armed electrodes 25 a, 25 b are interdigitated between each other.

Referring to the FIG. 3, the light-emitting device 3 includes an n-type electrode having a first contact 35 and an n-type fingered electrode 36 connected with the first contact 35 at a first side of the light-emitting device 3, a p-type electrode having a second contact 37 and two fingered electrodes 38 a, 38 b connected with the second contact 37 at a second side of the light-emitting device 3, wherein the first side and the second side are opposite to each other. The n-type fingered electrode 36 is extended from the first side to the second side, the p-type fingered electrodes 38 a, 38 b are extended from the second side to the first side, and the n-type fingered electrode 36 and the p-type fingered electrodes 38 a, 38 b are interdigitated between each other. The light-emitting devices 2 and 3 can resolve the current crowding and low light efficiency problems of the conventional light-emitting device 1 by the interdigitated extending electrodes.

Referring to FIG. 4, further another known art disclosed a light-emitting device 4. The epitaxial structure of the light-emitting device 4 includes a spiral-shaped trench, a p-type metal electrode 41 located in the exposed surface of the trench, an n-type metal electrode 42 located on the un-trenched surface of the epitaxial structure, a p-type bonding pad 43, and an n-type bonding pad 44, wherein the p-type metal electrode 41 and the n-type metal electrode 42 are parallel and distributed in spiral shape, which can resolve the current crowding and low light efficiency problems of the conventional light-emitting device 1

In above conventional light-emitting devices, the designs of electrodes adopt transparent electrodes or decrease the electrode area such as armed, fingered and spiral-shaped electrodes to optimize the light extraction area. In general, the width of an electrode is designed to be smaller than that of a bonding pad to avoid increasing the light absorption area of the electrode.

SUMMARY OF THE APPLICATION

Accordingly, this application provides a light-emitting device. The light-emitting device comprises a substrate; a light-emitting stack disposed on the substrate, comprising a first layer, a second layer, and a light-emitting layer disposed therebetween; a trench formed through the second layer, the light-emitting layer to the first layer wherein a part of the first layer is exposed; a first conductive structure disposed on the exposed part of the first layer in the trench; and a second conductive structure disposed on the second layer; wherein the first conductive structure comprises a first electrode and a first pad with an electrical connection formed therebetween; the second conductive structure comprises a second electrode and a second pad with an electrical connection formed therebetween; wherein at lease one of the first pad and the second pad has an area between 1.5×10⁴ μm² to 6.2×10⁴ μm².

This application also provides a light-emitting device comprising a substrate; a light-emitting stack disposed on the substrate comprising a first layer, a second layer, and a light-emitting layer disposed therebetween; a trench formed through the second layer, the light-emitting layer to the first layer wherein a part of surface of the first layer is exposed; a first conductive structure disposed on the exposed surface of the first layer in the trench; and a second conductive structure disposed on the second layer; wherein the first conductive structure comprises a first electrode and a first pad with an electrical connection formed therebetween; the second conductive structure comprises a second electrode and a second pad with an electrical connection formed therebetween; wherein at lease one of the first pad and the second pad comprises two bonding regions.

This application provides a light-emitting device comprising a substrate; a light-emitting stack disposed on the substrate comprising a first layer, a second layer, and a light-emitting layer disposed therebetween; and a first conductive structure disposed on the light-emitting stack wherein the first conductive structure comprises a first electrode and a first pad with an electrical connection formed therebetween; wherein the first pad comprises at least two bonding regions, or the area of the first pad is between 1.5×10⁴ μm² to 6.2×10⁴ μm².

This application provides a light-emitting device comprising a substrate; a light-emitting stack disposed on the substrate; and a first electrode and a first pad with an electrical connection formed therebetween; wherein the area of the first pad is between 3×10⁴ μm² to 1.24×10⁵ μm² and is capable of accommodate at least two wires.

This application provides a light-emitting device comprising a conductive substrate, an adhesive layer on the conductive substrate, a reflection layer on the adhesive layer, a second semiconductor layer on the reflection layer, a light-emitting layer on the second semiconductor layer, a first semiconductor layer on the light-emitting layer, a least one trench through the first semiconductor layer, and a first conductive structure on the first semiconductor layer, wherein the first conductive structure comprises a first electrode and a first pad.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide easy understanding of the application, and are incorporated herein and constitute a part of this specification. The drawings illustrate embodiments of the application and, together with the description, serve to illustrate the principles of the application.

FIGS. 1A-1B are a schematic top view and a cross-sectional view of a conventional light-emitting device 1.

FIG. 2 is a schematic cross-sectional view of a conventional light-emitting device 2.

FIG. 3 is a schematic cross-sectional view of a conventional light-emitting device 3.

FIG. 4 is a schematic cross-sectional view of a conventional light-emitting device 4.

FIGS. 5A-5C are a schematic top view and cross-sectional views of a light-emitting device in accordance with a first embodiment of the present application.

FIGS. 6A-6B are a schematic top view and a cross-sectional view of a light-emitting device in accordance with a second embodiment of the present application.

FIG. 7 is a schematic cross-sectional view of a light-emitting device in accordance with a third embodiment of the present application.

FIGS. 8A-8B are a schematic top view and a cross-sectional view of a light-emitting device in accordance with a fourth embodiment of the present application.

FIGS. 9A-9H are schematic cross-sectional views of a light-emitting device in accordance with a fifth embodiment of the present application.

FIGS. 10A-10F are schematic top views of the light-emitting device in accordance with a fifth embodiment of the present application.

FIG. 11 is a schematic cross-sectional view of a light source element including a light-emitting device of the present application.

FIG. 12 is a schematic cross-sectional view of a backlight module including a light-emitting device of the present application.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

Referring to FIG. 5A, the schematic top view shows a light-emitting device 10 in accordance with a first embodiment of the present application. FIG. 5B illustrates a cross-sectional view of the light-emitting device 10 along the B-B′ line in the FIG. 5A. The light-emitting device 10 such as an LED includes a substrate 100, a buffer layer 110, a first semiconductor layer 120, a light-emitting layer 130, a second semiconductor layer 140, a first electrode 151, a second electrode 152, a first and second pad 161 and 162. In the embodiment, the shape of light-emitting device 10 is a rectangular cube. Each side of the light-emitting device 10 is about 610 μm in length. The area of the top surface is 3.72×10⁵ μm², and the area of the light-emitting layer 130 is accorded with the area of the top surface. The buffer layer 110, first semiconductor layer 120, light-emitting layer 130, and second semiconductor layer 140 are formed on the substrate 100 by the method of metal organic chemical vapor deposition (MOCVD) or molecular-beam epitaxy (MBE).

After forming the epitaxial structure, an etching step is performed. A trench 170 is formed in the epitaxial structure by etching the epitaxial structure. A part of the first semiconductor layer 120 is exposed through the trench 170. The trench 170 is formed in a rectangular spiral shape, and the un-etched epitaxial structure is also formed in a rectangular spiral shape.

Next, the first electrode 151 and the first pad 161 are formed on the exposed surface of the first semiconductor layer 120. The shape of first electrode 151 is the same as the rectangular spiral shape of the trench 170, and the width of the first electrode 151 is about 22 μm. The position of first pad 161 can be between two end points of the first electrode 151 or in a non-end portion of the first electrode 151. In this embodiment, the first pad 161 is disposed at the non-end portion of the first electrode 151. Because the light-emitting device 10 has a larger light-emitting area, a larger operating current is necessary for a higher emitting efficiency. In order to achieve the larger amount of injected current, more pads area for current injecting are necessary. In this embodiment, the area of the first pad 161 is designed to be capable of containing at least two wires for current injecting, and the light-emitting device has enough wires for current injecting to improve the light-emitting efficiency. The area of the first pad 161 is 1.9×10⁴ μm²′ in the embodiment.

Further, the second electrode 152 and the second pad 162 are formed and connected with each other on the remained epitaxial structure. The width of the second electrode 152 is about 20 μm, and the shape of it is a rectangular spiral. The second pad 162 can be situated between two end points of the second electrode 152 or on a non-end portion of the second electrode 152. In this embodiment, the second pad 162 is situated on the non-end portion of the second electrode 152. Similarly, in order to achieve a larger injected current, in this embodiment, the area of the second pad 162 is designed to be capable of containing at least two wires for current injecting, thus the light-emitting device has enough amounts of wires for current injecting to improve the light-emitting efficiency. The area of the second pad 162 is 1.73×10⁴ μm² in the embodiment.

The shapes of the first pad 161 and the second pad 162 include rectangular shape, circular shape, or any other shapes. The first pad 161 and the second pad 162 including bonding regions are disposed on the first and the second electrodes respectively. In the embodiment, both shapes of the first pad 161 and the second pad 162 are two overlapped circles. Bonding regions 161A and 161B of the first pad 161, and bonding regions 162A and 162B of the second pad 162 can provide a better identification and avoid duplicate bonding of two wires on the same pad. There are wires connecting to the bonding regions 161A, 161B, 162A, and 162B respectively so the light-emitting device receives enough current by wires to have sufficient electrons and holes to recombine and then emits light. Referring to FIG. 5C, the schematic cross-sectional view shows a pad 161 with Au bonding bulges 180A and 180B formed on the bonding regions 161A and 161B respectively. During the bonding process, Au bulges are melted by raising temperature, and then the wires 171A and 171B are bonded with Au bonding bulges 180A and 180B respectively. Similarly, other two wires are bonded at the bonding regions 162A and 162B by the same method.

The direction of the spiral shape is clockwise or counterclockwise, and the numbers of spiral are not limited. The material of the substrate 100 includes but is not limited to sapphire. The material of the buffer layer 110 includes but is not limited to AlN, AlGaN, or GaN. The material of the first semiconductor layer 120 includes but is not limited to (Al_(x)Ga_(1-x))_(y)In_(1-y)N wherein 0≦x≦1 and 0≦y≦1. The light-emitting layer 130 includes but is not limited to a double heterostructure or a multi-quantum well including materials such as (Al_(p)Ga_(1-p))_(q)In_(1-q)N wherein 0≦p≦1 and 0≦q≦1. The material of the second semiconductor layer 140 includes but is not limited to (Al_(a)Ga_(1-a))_(b)In_(1-b)N wherein 0≦a≦1 and 0≦b≦1.

The material of the first electrode 151 is selected from materials which can be formed an ohmic contact with the first semiconductor layer 120, such as a single layer, multiple layers or alloy selected from Ti, Al, and Au, or other metal-oxide conductive material. The first Dad 161 includes but is not limited to a single layer, multiple layer or alloy selected from Ti, Al, and Au. The material of the second electrode 152 is selected from materials which can be formed an ohmic contact with the second semiconductor layer 140, such as a single layer, multiple layers or alloy selected from Ni and Au, or other metal-oxide conductive material. The second pad 162 includes but is not limited to a single layer, multiple layer or alloy selected from Ni and Au.

The areas of the first pad 161 and the second pad 162 do not need to satisfy the condition of having the area capable of accommodating at least two wires for current injecting at the same time. It can be one of the first pad 161 and the second pad 162 satisfying the condition that the area of pad is capable of containing at least two wires.

Referring to FIG. 6A, the schematic top view shows a light-emitting device 20 in accordance with a second embodiment of the present invention. FIG. 6B illustrates a cross-sectional view of the light-emitting device 20 along the C-C′ line in the FIG. 6A. The light-emitting device 20 includes a substrate 200, an adhesive layer 210, a current conductive layer 280, a first semiconductor layer 220, a light-emitting layer 230, a second semiconductor layer 240, a first electrode 251, a second electrode 252, a first and second pad 261 and 262. In the embodiment, the shape of the light-emitting device 20 is a rectangular cube, and the length of each side is about 787 μm. The area of the top surface is 6.19×10⁵ μm², and the area of the light-emitting layer 230 is in accord with the area of the top surface. The epitaxial structure of the light-emitting device 20 is formed on a growth substrate (not illustrated). After the epitaxial structure is grown, a current conductive layer 280 with a high current conductivity is fouled on the first semiconductor layer 220, which can spread the current injected from the electrode. Next, the epitaxial structure and the substrate 200 are adhered together by the adhesive layer 210.

After the adhering step, a trench 270 is formed in the epitaxial structure by etching the epitaxial structure. A part of the current conductive layer 280 is exposed through the trench 270. The trench 270 is formed in a fingered shape; the finger is extended from the first side to the opposite second side of the light-emitting device 20. The un-etched epitaxial structure also forms a fingered shape.

Next, the first electrode 251 and the first pad 261 are framed on the exposed surface of the current conductive layer 280. The shape of the first electrode 251 is the same as the fingered shape of the trench 270, and the first electrode 251 includes at least three linearly extending electrodes and a laterally extending electrode connected the three linearly extending electrodes. The width of the first electrode 251 is about 23 μm. The first pad 261 can be situated between two end points of the first electrode 251 or on a non-end portion of the first electrode 251. In this embodiment, the first pad 261 is situated on the non-end portion of the first electrode 251. Similarly, in order to achieve a higher emitting efficiency, in this embodiment, the area of the first pad 261 is designed to be capable of containing at least two wires for current injecting so the light-emitting device 20 has enough wires for current injection. The area of the first pad 261 is 2.15×10⁴ μm² in the embodiment.

Further, the second electrode 252 and the second pad 262 are formed and connected with each other on the remained epitaxial structure. The second electrode 252 includes three linearly extending electrodes extended from the second side to the opposite first side of the light-emitting device 20, and interdigitated between the three linearly extending electrode of the first electrode 251, and a laterally extending electrode connecting the three linearly extending electrodes. The width of the second electrode 252 is about 20 μm. The second pad 262 is disposed at the second side and connected with the second electrode 252. The area of the second pad 262 is 1.27×10⁴ μm² in the embodiment.

In this embodiment, the shape of the second pad 262 is rectangular, and the second pad 262 is situated on the non-end portion of the second electrode 152. The first pad 261 is capable of containing two bonding regions 261A and 261B. Each of regions 261A and 261B electrically connects to at least a wire for bonding, such that a better identification can be achieved for the next bonding procedure to avoid different wires being bonded at the same bonding region. The second pad 262 has a circular shape, and only one bonding region 262A which connects to a wire electrically. The area of the second pad 262 is also can be designed as an size containing at least two wires, such as the area of the second pad 262 is 1.5×10⁴ μm².

The material of the growth substrate includes but is not limited to sapphire, SiC, GaN, GaAs, or GaP. The material of the substrate 200 includes but is not limited to SiC, GaN, GaP, Si, AIN, ZnO, MgO, MgAl₂O₄, GaAs, glass, sapphire, metal, or compound materials. The adhesive layer 210 includes a conductive adhesive layer or an insulating adhesive layer. The material of the conductive adhesive layer includes but is not limited to Ag, Au, Al, In, or Sn, or alloy of them, spontaneous conductive polymer, or polymer doped with metal like Al, Au, Pt, Zn, Ag, Ni, Ge, In, Sn, Ti, Pb, Cu, Pd, or other metals. The material of the insulating adhesive layer includes but is not limited to spin on glass (SOG), silicone, benzocyclobutene (BCB), epoxy, polyimide (PI), or perfluorocyclobutane (PFCB). When the adhesive layer 210 is the insulating adhesive layer, the material of the substrate 200 is not limited. In the embodiment, the material of the substrate 200 is Si. The material of Si has a higher heat transfer coefficient to transfer the heat produced by the light-emitting device to the environment. A reflective layer is further disposed on one side of the adhesive layer 210. The material of the reflective layer includes but is not limited to metal, oxide, or the combination thereof. The oxide material for the reflective layer includes but is not limited to AlO_(x), SiO_(x), or SiN_(x).

When the adhesive layer 210 is the conductive adhesive layer, the material of the substrate 200 includes but is not limited to glass, sapphire, or AlN. It also can disposes an insulating layer between the current conductive layer 280 and the adhesive layer 210, or the adhesive layer 210 and the substrate 200, wherein the material of the substrate 200 is not limited. Referring to FIG. 7, a cross-sectional view shows a light-emitting device in accordance with a third embodiment of the present invention. FIG. 7 illustrates an insulating layer 690 disposed between the adhesive layer 210 and the current conductive layer 280 for isolation. The material of the insulating layer includes but is not limited to SiN_(x) or SiO₂. The material of the first semiconductor layer 220 includes but is not limited to (Al_(m)Ga_(1-m))_(r)In_(1-r)N wherein 0≦m≦1 and 0≦r≦1 or (Al_(c)Ga_(1-c))_(d)In_(1-d)P wherein 0≦c≦1 and 0≦d≦1. The light-emitting layer 230 includes but is not limited to a double heterostructure or a multi-quantum well including materials such as (Al_(e)Ga_(1-e))_(f)In_(1-f)N wherein 0≦e≦1 and 0≦f≦1 or (Al_(i)Ga_(1-i))_(j)In_(1-j)P wherein 0≦i≦1 and 0≦j≦1. The material of the second semiconductor layer 240 includes but is not limited to (Al_(k)Ga_(1-k))_(p)In_(1-p)N wherein 0≦k≦1 and 0≦p≦1 or (Al_(s)Ga_(1-s))_(t)In_(1-t)P wherein 0≦s≦1 and 0≦t≦1.

The material of the first electrode 251 includes but is not limited to a single metal layer, multiple metal layers or alloy of Ni, and Au, or other conductive metal oxide layer. The material of first pad 261 includes but is not limited to a single metal layer, multiple metal layers or alloy of Ni, and Au. The material of the second electrode 252 includes but is not limited to a single metal layer, multiple metal layers or alloy of Ti, Al, and Au, or conductive metal oxide layer. The second pad 262 includes but is not limited to a single metal layer, multiple metal layers or alloy of Ti, Al, and Au. The shapes of the first electrode 251 and the second electrode 252 include M linearly extending electrodes respectively, wherein M≧1. The first electrode 251 can include M linearly extending electrodes, wherein M≧1, and the second electrode 252 includes M−1 linearly extending electrodes.

Referring to FIG. 8A, the schematic top view shows a light-emitting device 30 in accordance with a fourth embodiment of the present invention. FIG. 8B illustrates a cross-sectional view of the light-emitting device 30 along the D-D′ line in the FIG. 8A. The structure of the light-emitting device 30 is similar to that of the light-emitting device 10 including a substrate 100, a buffer layer 110, a first semiconductor layer 120, a light-emitting layer 130, and a second semiconductor layer 140. After forming the epitaxial structure, a current conductive layer 380 is disposed on the second semiconductor layer 140. In the embodiment, the light-emitting device 300 is a rectangular cube and the length of each side of the light-emitting device 30 is about 1143 μm. The area of the top surface is 1.3 1×10⁶ μm², and the area of the light-emitting layer 130 is in accord with the area of the top surface.

After the step of forming the current conductive layer 380, an etching step is performed. A trench 370 is formed in the current conductive layer 380 and the epitaxial structure by etching part of them. A part of the first semiconductor layer 120 is exposed through the trench 370. The shape of the trench 370 is formed in a pair of spiral, and the un-etched current conductive layer 380 and epitaxial structure are also formed in a pair of spiral shape.

Referring to HG. 8A, the light-emitting device 30 includes a pair of first electrodes 351A and 351B and a pair of second electrodes 361A and 361B formed in a pair of spiral shape respectively. After the trench 370 is formed, the first electrodes 351A and 351B, and first pads 361A and 361B are formed on the exposed surface of the first semiconductor layer 120. The shape of first electrodes 351A and 351B are the same as the pair of spiral shape of the trench 370. The width of the first electrodes 351A or 351B is about 10 μm respectively. First pads 361A and 361B can be situated between two end points of first electrodes 351A and 351B or on a non-end portion of first electrodes 351A and 351B. In this embodiment, first pads 361A and 361B are situated on the non-end portions of first electrodes 351A and 351B near a first side of the light-emitting device 30 and a second side opposite to the first side. The area of first pad 361A and 361B are the same as 1.9×10⁴ μm².

Further, the second electrodes 352A and 352B, and the second pad 362 are formed on the remained current conductive layer 380. The width of the second electrode 352A or 352B is about 10 μm respectively. The second electrodes 352A and 352B are formed in a spiral shape and connected with the second pads 362 respectively. The second pad 362 can be disposed at a third side neighboring with the first side and the second side, and connect to second electrodes 352A and 352B. In this embodiment, the area of the second pad 362 is designed to be capable of containing at least two wires for current injection so the light-emitting device 30 has enough current to higher brightness. The area of the second pad 362 is 1.9×10⁴ μm² in the embodiment.

In the embodiment, the shape of the second pad 362 formed as two circles partially overlapped includes two bonding region 362A and 362B such that a better identification can be achieved for the next bonding procedure to avoid two wires being bonded on the same bonding region. There are wires connecting to the bonding regions 361A, 361B, 362A, and 362B respectively, so the light-emitting device 30 receives enough current by wires to have sufficient electrons and holes to recombine and then emits light. The shape of the light-emitting device 30 includes but is not limited to a square shape or a rectangular shape. The material of the current conductive layers 280 and 380 includes but is not limited to indium tin oxide, cadmium tin oxide, zinc oxide, or zinc tin oxide. Each surface of the light-emitting device can be a rough surface by an epitaxial or an etching process, such as a rough surface around the substrate or around the epitaxial structure, a rough surface in the top light extraction surface, or a rough surface under and contact with the electrode, to improve the light extraction efficiency.

The above mentioned embodiments from the first embodiment to the fourth embodiment of the present application are horizontal light-emitting device structures, wherein the first conductive structure and the second conductive structure are at the same side of the substrate. A fifth embodiment of the present application is a vertical light-emitting device structure, wherein the first conductive structure and the second conductive structure are at the opposite sides of the substrate. The fifth embodiment of the present application discloses a light-emitting device 50 comprising a conductive substrate 521, an adhesive layer 506 on the conductive substrate 521, a reflection layer 505 on the adhesive layer 506, a second semiconductor layer 504 on the reflection layer 505, a light-emitting layer 503 on the second semiconductor layer 504, a first semiconductor layer 502 on the light-emitting layer 503, at least one trench 508 through the first semiconductor layer 502, and a first conductive structure 512 on the first semiconductor layer 502, wherein the first conductive structure 512 comprises a first electrode 514 and a first pad 513, as shown in FIGS. 9H, and 10A-10F. The method of forming a light-emitting device 50 comprises providing a growth substrate 501, as shown in FIG. 9A, and growing a first semiconductor layer 502, a light-emitting layer 503, and a second semiconductor layer 504 in sequence on the growth substrate 501 by the metal-organic chemical vapor deposition (MOCVD) method, as shown in FIG. 9B. The growth substrate 501 mentioned above can be sapphire. The first semiconductor layer 502, the light-emitting layer 503 and the second semiconductor layer 504 mentioned above comprise III-V group compound such as AlGaInN series material.

Referring to FIG. 9C, a reflection layer 505 is formed on the second semiconductor layer 504. Referring to FIG. 9D, a conductive substrate 521 is provided, and an adhesive layer 506 is formed on the conductive substrate 521. The conductive substrate 521 can be Si, Ge, Cu, Mo, and ZnO. As indicated in FIG. 9E, the reflection layer is connected with the conductive substrate by the adhesive layer. The growth substrate 501 is removed by laser irradiation 522, then the structure 40 is formed as FIG. 9F shows. The adhesive layer 506 comprises soldering tin, low temperature metal, metal silicides, PbSn, AuGe, AuBe, AuSi, Sn, In, and PdIn. The reflection layer 505 comprises Ag, Al, Zn, Mg, Ru, Ti, Rh, Cr, and Pt.

As FIG. 9G shows, a mask layer 507 is formed on the first semiconductor layer 502, such that a portion of the first semiconductor layer 502 is covered by the mask layer 507. Other portion of the first semiconductor layer 502 not covered by the mask layer 507 is etched by inductively coupled plasma (ICP) etching 523. As FIG. 9H shows, at least one trench 508 is formed. After removing the mask layer 507, a plurality of platforms 509 are formed. At least one trench 508 is formed through the first semiconductor layer 502 and a plurality of platforms 509 are formed on the first semiconductor layer 502. Finally, a first conductive structure 512 is formed on the platforms 509 so the light-emitting device 50 is formed. The first conductive structure 512 comprises Ni, Au, Pt, Pd, Mg, Cu, Zn, Ag, Sc, Co, Rh, Li, Be, Ca, Ru, Re, Ti, Ta, Na, and La. FIGS. 10A-10F show the top views of the light-emitting device 50. The first conductive structure 512 comprises a first electrode 514 and a first pad 513 where in the area of the first pad 513 is between 1.5×10⁴ μm² and 6.2×10⁴ μm² in the embodiment. The conductive substrate 521 is electrically connecting with the second semiconductor layer 504, so it can be used for a second conductive structure of the light-emitting device 50.

The first semiconductor layer 502 has a thickness H, and the trench 508 has a depth h. TABLE.1 shows the differences between the light output power (IV) and the depth of the trench (h) in the light emitting device 50. As TABLE.1 shows, Sample no. 0 is a reference sample having a depth of the trench h of 0, which means the first semiconductor layer 502 has no trenches. The light output power of the Sample no. 0 is 455 mW. The h of the Sample no 1 is between 0 and H/3, and the light output power is 455.91 mW. The difference of light output power between the Sample no. 0 and 1, ΔIv, equals to [(455.91−455)×100%]/455, and the ΔIv value of the Sample no. 1 is 0.2%. The h of the Sample no. 2 is between H/3 and 2H/3, and the light output power is 461.37 mW. The difference of light output power between the Sample no. 0 and 2, ΔIv, equals to [(461.37-455)×100%]/455, and the ΔIv value of the Sample no. 2 is 1.4%. The h of the Sample no. 3 is between 2H/3 and H, and the light output power is 463.65 mW. The difference of light output power between the Sample no. 0 and 3, ΔIv, equals to [(463.65−455)×100%]/455, and the ΔIv value of the Sample no. 3 is 1.9%. The h of the Sample no. 4 is greater than H, and the light output power is 439.99. The difference of light output power between the Sample no. 0 and 4, ΔIv, equals to [(439.99−455)Δ100%]/455, and the ΔIv value of the Sample no. 4 is −3.3%.

TABLE 1 Sample no. h (μm) Iv (mW) ΔIv (%) 0 0 455 — 1 0 < h ≦ H/3 455.91 0.2 2 H/3 < h ≦ 2H/3 461.37 1.4 3 2H/3 < h ≦ H 463.65 1.9 4 h > H 439.99 −3.3

TABLE.1 shows that when the h is between H/3 and H, the difference of the light output power with Sample No. 0 increases. But when the h is greater than H, the difference of the light output power with Sample No. 0 decreases. One reason the light output power of the light-emitting device 50 increases is the area of the sidewall of the trenches 508 is enlarged when the depth h of the trenches 508 is increased, and the light output power is also increased. Another reason the light output power of the light-emitting device 50 increases when the depth of the trenches h is increasing is that the thickness of the first semiconductor layer 502 in the trenches is decreased so the light absorbed by the first semiconductor layer 502 is also decreased. In other words, the larger the depth of the trenches 508 is, the higher the light output of the light-emitting device 50 has. But when the depth of the trenches 508 is greater than H, it means that inductively coupled plasma (ICP) etching 523 etches the portion of the first semiconductor layer 502 from the top surface of the first semiconductor layer 511 to the light-emitting layer 503. Because the light-emitting layer 503 is etched, the light output of the light-emitting device 50 is decreased.

Because the first semiconductor layer 502 serves to spread current, it can not be etched too much. If the area of the top surface of the first semiconductor layer 511 is 1 mm², the area of the a plurality of platforms 509 is preferred to be greater than a half of the area of the top surface of the first semiconductor layer 511, ie. 0.5 mm². FIGS. 10A and 10B show top views of the trenches 508 of a plurality of circles formed through the first semiconductor layer 502, and the depth h of the trenches 508 are between H/3 and H, wherein H is the thickness of the first semiconductor layer 502. The platforms 509 are the area other than the plurality of trenches 508, and the first conductive structure 512 comprises a first electrode 514 encompassing the edge and central regions of the light-emitting device and a first pad 513. In the embodiment, the area of the platforms 509 is preferred to be greater than a half of the area of the top surface of the first semiconductor layer 511, and the area of the first pad 513 is between 1.5×10⁴ μm² and 6.2×10⁴ μm². FIG. 10C shows a top view of the trenches 508 of two stripes with round corners formed through the first semiconductor layer 502 and between the first electrodes 514, and the depth h of the trenches are between H/3 and H, wherein H is the thickness of the first semiconductor layer 502. The platforms 509 are the area other than the two trenches 508, and the first conductive structure 512 comprises two first electrodes 514 and two first pads 513. In the embodiment, the area of the platforms 509 is preferred to be greater than a half of the area of the top surface of the first semiconductor layer 511, and the area of the first pads 513 is between 1.5×10⁴ μm² and 6.2×10⁴ μm². FIG. 10D shows a top view of the trench 508 of one stripe with round corners formed through the first semiconductor layer 502 and between the first electrodes 514, and the depth h of the trenches are between H/3 and H, wherein H is the thickness of the first semiconductor layer 502. The platforms 509 are the area other than the trench 508, and the first conductive structure 512 comprises two first electrodes 514 encompassing the edge regions of the light-emitting device and two first pads 513. In the embodiment, the area of the platforms 509 is preferred to be greater than a half of the area of the top surface of the first semiconductor layer 511 and the area of the first pads 513 is between 1.5×10 μm² and 6.2×10⁴ μm². FIG. 10E shows a top view of the trenches 508 of two stripes formed through the first semiconductor layer 502 and between the first electrodes 514, and the depth h of the trenches are between H/3 and H, wherein H is the thickness of the first semiconductor layer. The platforms 509 are the area other than the two trenches 508, and the first conductive structure 512 comprises two first electrodes 514 encompassing the edge and central regions of the light-emitting device and two first pads 513. In the embodiment, the area of the platforms 509 is preferred to be greater than a half of the area of the top surface of the first semiconductor layer 511, and the area of the first pad 513 is between 1.5×10⁴ μm² and 6.2×10⁴ μm². FIG. 10F shows a top view of the trenches 508 of two stripes with round corners formed through the first semiconductor layer 502 and between the first electrodes 514, and the depth h of the trenches are between H/3 and H, wherein H is the thickness of the first semiconductor layer 502. The platforms 509 are the area other than the two trenches 508, and the first conductive structure 512 comprises three first electrodes 514 and one first pad 513. In the embodiment, the area of the platforms 509 is preferred to be greater than a half of the area of the top surface of the first semiconductor layer 511, and the area of the first pad 513 is between 1.5×10⁴ μm² and 6.2×10⁴ μm².

Referring to FIG. 11, the schematic cross-sectional view shows a light source apparatus 90 in accordance with a sixth embodiment of the present application. The light source apparatus 90 includes a light-emitting device of above embodiments. The light source apparatus 7 is a lighting apparatus such as streetlamps, vehicle lamps, or indoor lightings. It also can be traffic lights or backlights of a module in a planar display. The light source apparatus 90 includes a light source 910 with the light-emitting device of above embodiments, a power supply system 920, and a control element 930 for controlling the power supply system 920.

Referring to FIG. 12, the schematic cross-sectional view shows a backlight module 95 in accordance with a seventh embodiment of the present application. The backlight module 95 includes the light source apparatus 90 and an optical element 1010. The optical element 1010 is used to operate the light emitted from the light source apparatus 90 to satisfy the requirements of the backlight. The optical element 1010 includes a photonic lattice, a color filter, a wavelength conversion layer, an antireflective layer, a lens or the combination thereof.

It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present application without departing from the scope or spirit of the application. In view of this, it is intended that the present application covers modifications and variations of this application provided they fall within the scope of the following claims and their equivalents. 

What is claimed is:
 1. A light-emitting device comprising: a substrate; an adhesive layer on the substrate; a reflection layer on the adhesive layer; a second semiconductor layer on the reflection layer; a light-emitting layer on the second semiconductor layer; a first semiconductor layer on the light-emitting layer, wherein a thickness of the first semiconductor layer is H; a plurality of trenches through the first semiconductor layer, wherein a depth of one of the plurality of trenches is h; and a first conductive structure on the first semiconductor layer; wherein the depth of the trench h is greater than ⅓ of the thickness of the first semiconductor layer H; wherein the first conductive structure comprises a first electrode encompassing an edge region of the light-emitting device, and wherein a total area of all trenches in the first semiconductor layer is not greater than 50% of an area of a top surface of the first semiconductor layer.
 2. The light-emitting device according to claim 1, wherein the at least one trench is formed by removing a portion of the top surface of the first semiconductor layer.
 3. The light-emitting device according to claim 1, wherein the depth of the trench h is not greater than the thickness of the first semiconductor layer H.
 4. The light-emitting device according to claim 1, wherein the first conductive structure comprises a first pad connecting with the first electrode.
 5. The light-emitting device according to claim 4, wherein an area of the first pad is between 1.5×10⁴ μm² and 6.2×10⁴ μm².
 6. The light-emitting device according to claim 4, wherein the first conductive structure further comprises a second pad.
 7. The light-emitting device according to claim 1, wherein the plurality of trenches forms a two-dimensional array.
 8. The light-emitting device according to claim 1, wherein a top view of one of the plurality of trenches comprises a circle.
 9. A light-emitting device comprising: a substrate; a second semiconductor layer on the substrate; a light-emitting layer on the second semiconductor layer; a first semiconductor layer on the light-emitting layer; a plurality of trenches in the first semiconductor layer; and a first conductive structure comprising a plurality of first electrodes and a first pad on the first semiconductor layer; wherein a depth of one of the plurality of trenches is greater than one-third of a thickness of the first semiconductor layer but less than the thickness of the first semiconductor layer; wherein the plurality of trenches is formed between two of the plurality of first electrodes, and wherein a total area of all trenches in the first semiconductor layer is not greater than 50% of an area of a top surface of the first semiconductor layer.
 10. The light-emitting device according to claim 9, further comprising another trench in the first semiconductor layer, wherein the another trench is formed between two of the plurality of first electrodes.
 11. The light-emitting device according to claim 9, wherein a top view one of the plurality of trenches comprises a stripe.
 12. The light-emitting device according to claim 11, wherein the stripe comprises a round corner.
 13. The light-emitting device according to claim 9, wherein an area of the first pad is between 1.5×10⁴ μm² and 6.2×10⁴ μm².
 14. The light-emitting device according to claim 9, wherein two of the plurality of first electrodes encompass an edge region of the light-emitting device, and another two of the plurality of first electrodes extend through a central region of the top surface of the first semiconductor layer.
 15. The light-emitting device according to claim 9, wherein the first conductive structure further comprises a second pad on the first semiconductor layer. 